JP2010026077A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which does not cause distortion of paper and has high productivity. <P>SOLUTION: The image forming apparatus 1 is equipped with: a secondary transfer belt 51 provided at a position opposed to an intermediate transfer belt 43b across a conveying path of paper P; a fixing belt 62 provided on a downstream side of the secondary transfer belt 51 in the conveying direction of the paper P and provided at a position opposed to a rotating fixing member 61 across the conveying path of the paper P; a photosensor 66 detecting a position in a width direction of the fixing belt 61; a steering roller angle changing part 70 capable of changing a turning angle of a steering roller 65; and a first control part 90 controlling a stepping motor 75 based on a signal from the photosensor 66. The control part 90 does not change the angle of the steering roller 65 when paper restraint is present in both a transfer nip and a fixing nip. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus.

  There is known an image forming apparatus in which a toner carried on an image carrier such as a photosensitive member or an intermediate transfer member is transferred onto a sheet in a transfer unit, and the toner transferred on the sheet is heated and fixed in a fixing unit.

FIG. 11 schematically shows a transfer unit 210 and a fixing unit 220 of a conventional image forming apparatus 200.
The transfer unit 210 includes a photosensitive drum 211 that carries toner, a transfer belt 212, and rollers 213, 214, and 215. The photosensitive drum 211 and the roller 213 are arranged so that the outer peripheral surfaces thereof face each other with the conveyance path of the paper P interposed therebetween. The sheet P is sandwiched between the photosensitive drum 211 and the transfer belt 212 at a portion where the photosensitive drum 211 and the roller 213 face each other, and is conveyed in the direction of the arrow. In this conveyance process, the toner image on the photosensitive drum 211 is transferred onto the paper P.

  The fixing unit 220 includes a fixing roller 221 having a heat source, a fixing belt 222, and rollers 223, 224, and 225. The fixing roller 221 and the roller 223 are arranged so that their outer peripheral surfaces face each other with the conveyance path of the paper P interposed therebetween. The sheet P is sandwiched between the fixing roller 221 and the transfer belt 222 from the portion where the fixing roller 221 and the roller 223 are opposed to the upstream side in the sheet P conveyance direction, and is conveyed in the direction of the arrow. During this conveyance process, the toner image on the paper P is heated and fixed by the fixing roller 221.

  The transfer belt 212 and the fixing belt 222 are operated by driving each roller provided in the ring. Each belt may be displaced in the width direction side of the belt during operation. The misregistration causes kinking, undulation, etc. of the belt, which may cause various defects such as poor contact between the photosensitive drum 211 or the fixing roller 221 and the paper P, image deviation, and rough gloss. In order to prevent the defect, the image forming apparatus is provided with a configuration for suppressing or correcting the displacement. For example, there is a configuration in which guide members are provided on both sides in the width direction of each belt to suppress belt position shift (for example, Patent Document 1). In addition, there is a configuration in which the angle with respect to the belt can be changed for any one of the rollers in the ring of each belt, and the position in the width direction of the belt is guided and controlled by changing the angle (for example, Patent Document 2).

  Among these, in the configuration in which the positional deviation in the width direction of the belt is suppressed by the guide member as in Patent Document 1, when the belt is largely displaced, the belt may move over the guide member and cause the positional deviation. . Therefore, when it is desired to control the position of the belt with certainty, a configuration is adopted in which position control in the width direction of the belt is performed by controlling the angle of the rollers as in Patent Document 2.

  In recent years, in order to reduce the size of the image forming apparatus, a position where the sheet P is sandwiched by the transfer unit 210 (hereinafter referred to as “transfer nip”) and a position where the sheet P is sandwiched by the fixing unit 220 (hereinafter referred to as “fixing nip”). There is an image forming apparatus in which the interval E is smaller than the width in the conveyance direction of the paper P. In this image forming apparatus, the timing at which the paper P is sandwiched between both the transfer nip and the fixing nip may occur. If the position control in the width direction of each belt is performed by the angle of the roller when the paper P is sandwiched between the transfer nip and the fixing nip, the paper P may be distorted. Hereinafter, the distortion will be described with reference to FIG.

  FIG. 12 shows an example in which distortion occurs in the paper P. The sheet P is sandwiched in the transfer unit 210 at the position of the transfer nip G, and is sandwiched in the fixing unit 220 at the position of the fixing nip H. At this time, when the position of the transfer belt 212 and the fixing belt 212 is controlled in different directions, the sheet P is pulled in opposite directions at the positions of the transfer nip G and the fixing nip H, and the transfer nip G and the fixing nip H Distortion occurs between the two. The distortion may cause toner fixing failure, and may cause various defects in image formation and quality deterioration such as paper P may be wrinkled by the fixing unit 220 while being distorted. Can be.

Therefore, when there is a sheet in the fixing unit, there is a configuration that prohibits the angle control of the roller for correcting the positional deviation of the belt (for example, Patent Document 3).
Japanese Patent Laid-Open No. 3-25477 JP-A-8-262903 Japanese Utility Model Publication No. 5-30854

  However, when the configuration of Patent Document 3 is used, the productivity of the image forming apparatus may decrease. This is because if the belt is misaligned so as to cause a defect in image formation, the transfer and fixing to the paper are temporarily interrupted even during the image forming process on the paper to control the belt position. This is because it must be done. In particular, when processing such as continuously forming images on a plurality of sheets is performed, the interruption significantly reduces the productivity of the image forming apparatus.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus with high productivity without causing paper distortion.

  An image forming apparatus according to a first aspect of the present invention includes a transfer unit provided on the upstream side in the sheet conveyance direction and having a transfer nip, a fixing unit provided on the downstream side in the conveyance direction and having a fixing nip by a fixing belt, and the fixing A fixing belt position changing mechanism that changes the position of the belt in the width direction; and a control unit that controls the fixing belt position changing mechanism according to the position of the fixing belt in the width direction. Is sandwiched between both the transfer nip of the transfer portion and the fixing nip of the fixing portion, the position in the width direction of the fixing belt is not changed.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the fixing belt position changing mechanism section includes a first steering roller that stretches the fixing belt, and the first steering roller. The position in the width direction of the fixing belt is changed by changing the rotation angle.

  According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the transfer unit having a transfer nip by a transfer belt, and a transfer belt position changing mechanism unit that changes a width direction position of the transfer belt; The control unit does not change the position in the width direction of the transfer belt when the sheet is sandwiched between both the transfer nip of the transfer unit and the fixing nip of the fixing unit. And

  According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, the transfer belt position changing mechanism includes a second steering roller that stretches the transfer belt, and the second steering roller. The position in the width direction of the transfer belt is changed by changing the rotation angle.

  According to a fifth aspect of the present invention, in the image forming apparatus according to the first or second aspect, the transfer unit has a transfer nip formed by a transfer roller.

  According to the present invention, it is possible to provide an image forming apparatus with high productivity without causing paper distortion.

(First embodiment)
Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic cross-sectional configuration diagram of an image forming apparatus 1 according to the first embodiment.

  As shown in FIG. 1, the image forming apparatus 1 reads an image from a document, forms a read image on a sheet P, and outputs it, page data including image data from an external device or the like, and each image data A print function for receiving a job including the image forming conditions, and forming and outputting an image on the paper P based on the received job. As shown in FIG. 1, the image forming apparatus 1 includes an image reading unit 20, a printing unit 40, and the like.

  The image reading unit 20 includes an automatic document feeder 21 called an ADF (Auto Document Feeder) and a reading unit 22. The document d placed on the document tray 21a of the automatic document feeder 21 is conveyed to a contact glass which is a reading location, and an image on one or both sides of the document d is read by an optical system, and a CCD (Charge Coupled Device) 22a. As a result, the image of the document d is read. Here, the image means not only image data such as graphics and photographs but also text data such as characters and symbols.

  The image (analog image signal) read by the image reading unit 20 is output to the control unit 90 to be described later, subjected to various image processing such as A / D conversion in the control unit 90, and then to the printing unit 40. Is output.

  The print unit 40 performs an electrophotographic image forming process based on the input print data, and includes a paper feed unit 41, a conveyance unit 42, an image formation unit 43, a fixing unit 60, an unloading unit 45, an unloading unit 45, and an unloading unit 45. A standby unit 46 is provided.

  The paper feed unit 41 includes a plurality of paper feed trays 41a, a paper feed unit 41b, a manual feed tray 41c, and the like. The paper feed tray 41a stores standard paper, special paper, insertion paper, and other paper P identified for each paper feed tray 41a on the basis of the amount and size of the paper for each preset type. The paper P is transported one by one from the top toward the transport unit 42 by the paper feeding means 41b. The manual feed tray 41c is a paper feed tray on which various types of paper P can be stacked according to the user's needs, and transports the paper P stacked by the paper feed rollers one by one from the top to the transport unit 42. To do.

  The transport unit 42 transports the paper P transported from the paper feed tray 41a or the manual feed tray 41c to the secondary transfer belt 51 through a plurality of intermediate rollers, registration rollers 42a, and the like. The registration roller 42a functions as a first standby unit that temporarily waits for a sheet conveyed to the secondary transfer belt 51. The secondary transfer belt 51 receives the toner image on the intermediate transfer member (intermediate transfer belt 43b). It functions as a secondary transfer section that performs secondary transfer onto the paper.

  Further, the conveyance unit 42 conveys the sheet P on which the single-sided image formation processing has been performed to the double-side conveyance path by the conveyance path switching plate, and conveys the sheet P again to the secondary transfer belt 51 through the intermediate roller and the registration roller 42a. By the secondary transfer belt 51, a toner image primarily transferred to an intermediate transfer belt 43b described later is secondarily transferred onto the paper P.

  For example, when forming an image of four colors (yellow (Y), magenta (M), cyan (C), and black (K)), the image forming unit 43 is provided for each color that can be filled with toner of different colors. The image forming units 43Y, 43M, 43C, and 43K, an intermediate transfer belt 43b, and a cleaning unit 50 are provided.

  For example, the image forming unit 43Y primarily transfers a charging device, an exposure device, a developing device, and a toner image on which an electrostatic latent image based on image data developed around the photosensitive drum is developed onto the intermediate transfer belt 43b. A primary transfer roller 43Ya that functions as a primary transfer unit and a cleaning device are provided to form a yellow (Y) image.

Specifically, an electrostatic latent image is formed by irradiating the photosensitive drum charged by the charging device with light according to yellow (Y) image data from the exposure device. The developing device develops the electrostatic latent image by attaching charged yellow (Y) toner to the surface of the photosensitive drum on which the electrostatic latent image is formed. The photosensitive drum to which toner is attached by the developing device is primarily transferred to the intermediate transfer belt 43b while being rotated at a constant speed to a transfer position where the primary transfer roller 43Ya is disposed. After the toner is primarily transferred to the intermediate transfer belt 43b, the cleaning device removes residual charges, residual toner, and the like on the surface of the photosensitive drum.

  The image forming units 43M, 43C, and 43K have the same configuration as the image forming unit 43Y, and form magenta (M), cyan (C), and black (K) images, respectively.

The intermediate transfer belt 43b is a semiconductive endless belt that is suspended and supported rotatably by a plurality of rollers, and is driven and moved with the rotation of a roller such as a drive roller.
The intermediate transfer belt 43b is pressure-bonded to the respective photosensitive drums by primary transfer rollers 43Ya, 43Ma, 43Ca, and 43Ka of the image forming units 43Y, 43M, 43C, and 43K. As a result, the toner developed on the surface of each photosensitive drum is primarily transferred to the intermediate transfer belt 43b at the transfer positions by the primary transfer rollers 43Ya, 43Ma, 43Ca, and 43Ka, and the paper is transferred to the sheet at the transfer position by the secondary transfer roller 52. Yellow, magenta, cyan, and black toners are sequentially superimposed on P and secondarily transferred. The secondary transfer roller 52 functions as a secondary transfer unit that secondary-transfers the toner image primarily transferred to the intermediate transfer belt 43b onto the paper P.

  The intermediate transfer belt 43b secondarily transfers the toner image onto the paper P by the secondary transfer roller 52, and then separates the paper P from the curvature and electrostatically, and the residual toner is removed by the cleaning unit 43d.

  The fixing unit 60 is a toner in which a rotary fixing member 61 having a heat source 61a and a fixing belt 62 that presses against the rotary fixing member 61 to form a fixing nip H1 (see FIG. 3) are secondarily transferred to the paper P. Fix the image by heating.

  The carry-out unit 45 includes a plurality of paper discharge rollers, a carry-out port 45a, and a paper discharge surface switching path 45b. The paper P on which the toner image is fixed is sandwiched between the paper discharge rollers by the conveyance path switching plate. A discharge function that functions as a paper discharge surface switching unit that switches the paper surface of the paper discharged from the outlet 45a to the carry standby unit 46, or the paper P on which the toner image is fixed is sandwiched between the paper discharge rollers. After being transported to the paper surface switching path 45b, it is unloaded from the unloading port 45a to the unloading standby unit 46.

  The carry-out standby unit 46 is provided between the secondary transfer roller 42b and the paper discharge tray 47, and includes a plurality of paper discharge rollers, a first carry-out path 46a, and a second carry-out path 46b. The sheet carried in from the carry-out port 45a is conveyed by the plate to the first carry-out path 46a or the second carry-out path 46b, and then discharged to the paper discharge tray 47.

  The first carry-out path 46a is a path for discharging the paper carried in from the carry-out port 45a to the paper discharge tray 47 on the same surface as the paper surface carried in from the carry-out port 45a. The second carry-out path 46b functions as a second standby unit that temporarily waits for the paper carried in from the carry-out port 45a, and is a path that discharges the paper to the paper discharge tray 47 at a predetermined timing. The first carry-out path 46a This is a path for discharging paper to the paper discharge tray 47 on the reverse side to the paper surface carried out to the paper discharge tray 47.

  A paper position detection unit 80 for recognizing the position of the paper P is provided on the upstream side of the secondary transfer belt 51 in the transport direction of the paper P. When the paper position detection unit 80 detects the passage of the paper P conveyed by the conveyance unit 42, the paper position detection unit 80 outputs a signal to that effect (hereinafter referred to as a detection signal). The detection signal is input to a control unit 90 (see FIG. 2) described later.

  FIG. 2 shows a functional block diagram of the image forming apparatus 1. The image forming apparatus 1 includes a control unit 90, a communication unit 110, an image memory 120, an operation display unit 130, photosensors 55 and 66, and stepping motors 75 and 76.

The control unit 90 includes a CPU 91, a RAM 92, a ROM 93, etc., which are connected to each other by a bus 94. The control unit 90 controls the operation of the image forming apparatus 1 by so-called software processing in which software corresponding to the processing content is called from the ROM 93 or the like, loaded into the RAM 92, and executed.
The control unit 90 is connected to the image reading unit 20, the printing unit 40, the paper position detection unit 80, the communication unit 110, the image memory 120, the operation display unit 130, the photosensors 55 and 66, the stepping motors 75 and 76, and the bus 150. The image forming apparatus 1 is controlled by controlling each unit based on the input of each unit.

  For example, when the detection signal of the paper position detection unit 80 is input, the control unit 90 calculates the position of the paper P based on the input timing of the detection signal and the elapsed time from the timing, and according to the position of the paper P Process.

  The communication unit 110 includes an interface (for example, a NIC (Network Interface Card) or the like) that can be connected to an external device (for example, a PC), and enables communication between the image forming apparatus 1 and the external device. For example, image data transmitted from a PC or the like is received by the image forming apparatus 1 via the communication unit 110 and stored in the image memory 120.

  The image memory 120 is a storage area for storing image data to be formed on the paper P by the image forming apparatus 1, and includes a storage device (for example, a volatile memory). Image data read from the image reading unit and image data transmitted via the communication unit 110 are stored in the image memory 120. The control unit 90 forms an image on the paper P based on the image data stored in the image memory 120.

  The operation display unit 130 includes an LCD (Liquid Crystal Display), a touch panel, and the like, and can display various information related to the image forming apparatus 1 and perform various input operations by an operator.

  The photo sensors 55 and 66 and the stepping motors 75 and 76 have a configuration related to the position control in the width direction of the secondary transfer belt 51 and the fixing belt 62. Hereinafter, the configuration of the secondary transfer belt 51 and the fixing belt 62 and the position control in the width direction will be described in detail.

FIG. 3 shows details of the secondary transfer unit and the fixing unit 60.
The secondary transfer belt 51 is an annular belt member, and a secondary transfer roller 52, a driven roller 53, and a steering roller 54 are disposed in the ring. The secondary transfer belt 51 is stretched by the cooperation of the secondary transfer roller 52, the driven roller 53, and the steering roller 54. The secondary transfer roller 52 rotates by driving a drive unit (not shown) such as a motor, and drives the secondary transfer belt 51. In the secondary transfer portion, a transfer nip G1 is formed in which the paper P is sandwiched between the secondary transfer belt 51 and the intermediate transfer belt 43b, and secondary transfer by the secondary transfer roller 52 is performed at this position.
A photo sensor 55 is provided between the secondary transfer roller 52 and the steering roller 54.

The fixing belt 62 is an annular belt member, and a fixing belt driving roller 63 that stretches the fixing belt 62, a driven roller 64, and a steering roller 65 are disposed in the ring. The fixing belt 62 is stretched by the cooperation of the fixing belt driving roller 63, the driven roller 64 and the steering roller 65. The fixing belt driving roller 63 rotates by driving a driving unit (not shown) such as a motor, and drives the fixing belt 62.
A photo sensor 66 is provided between the driven roller 64 and the steering roller 65.

  A pressure contact member 67 is provided at a position facing the rotary fixing member 61 with the fixing belt 62 interposed therebetween. The pressure contact member 67 is biased toward the rotation fixing member 61 by the elasticity of the spring 68. As a result, the rotation fixing member 61 and the fixing belt 62 cooperate to form a fixing nip H1 that sandwiches the paper P.

  In the direction along the conveyance direction of the paper P, the width between the transfer nip G1 and the fixing nip H1 is smaller than the maximum length in the direction along the conveyance direction of the paper P that can be used in the image forming apparatus 1. . That is, depending on the maximum length in the direction along the conveyance direction of the paper P, the paper P may be pinched by both the transfer nip G1 and the fixing nip H1.

Next, a mechanism for controlling the positions in the width direction of the secondary transfer belt 51 and the fixing belt 62 will be described based on the configuration relating to the position control of the fixing belt 62.
FIG. 4 is a perspective configuration diagram of the steering roller angle changing unit 70. The steering roller 65 is provided such that a contact angle with respect to the operation direction of the fixing belt 62 can be changed by the steering roller angle changing unit 70. The steering roller angle changing unit 70 includes a rotation member 71, a rotation gear 73, a support unit 74, and a stepping motor 75.

  The steering roller 65 is supported at one end 65 b of the shaft portion thereof by the U groove portion 71 a of the rotating member 71. The rotating member 71 is supported so as to be rotatable about a shaft portion 71b in the direction along the width direction of the fixing belt. The rotation member 71 has a gear portion 71 c that meshes with the rotation gear 73.

  The rotation gear 73 is connected to the stepping motor 75, and the rotation angle is displaced by driving the stepping motor 75. The rotation member 71 is rotated and supported at a rotation angle corresponding to the rotation angle of the rotation gear 73, thereby rotating and supporting one end 65 b of the steering roller 65.

  The other end 65 c of the shaft portion of the steering roller 65 is supported by a support portion 74 provided on a frame in the image forming apparatus 1. The support part 74 supports the steering roller 65 in a state in which the steering roller 65 is rotatably supported and the rotating member 71 can rotate the one end side of the steering roller 65. As a result, the one end 65b side of the steering roller 65 is provided so as to be able to rotate as indicated by an arrow Q shown in FIG. 2, and the arrangement angle of the fixing belt 62 with respect to the operating direction can be changed.

  FIG. 5 shows an explanatory diagram of the relationship between the shaft angle of the steering roller 65 and the fixing belt 62 when viewed from the V direction of FIG. In FIG. 5, a position where the center line in the width direction of the fixing belt 62 is desirably located is indicated by a dashed line L. A one-dot broken line L is, for example, a position in the width direction of the fixing belt 62 where the rotary fixing member 61 and the fixing belt 62 are best pressed against each other.

  When one end 65b of the steering roller 65 rotates in the operation direction F side of the fixing belt 62 relative to the other end 65c (the minus (−) direction in FIG. 5), the fixing belt 62 is guided to the other end 65c side of the steering roller 65. The On the other hand, when one end 65b of the steering roller 65 rotates in the direction opposite to the operation direction F of the fixing belt 62 with respect to the other end 65c (+ (plus) direction in FIG. 5), the fixing belt 62 is connected to one end 65b of the steering roller 65. Guided to the side. Accordingly, by controlling the rotation angle of the steering roller, the position in the width direction of the fixing belt 62 is corrected so that the center line thereof overlaps the one-dot broken line L.

FIG. 6 shows the positional relationship between the photo sensor 66 and the fixing belt 62. FIG. 6 is a WW sectional view of FIG.
As shown in FIG. 6, the photo sensor 66 includes light emitting elements S1 to S3 and light receiving elements R1 to R3. The light emitting elements S1 to S3 and the light receiving elements R1 to R3 are provided at positions facing each other with the fixing belt 62 interposed therebetween. The light emitting elements S1 to S3 irradiate light (for example, infrared rays) toward the light receiving elements R1 to R3, respectively. The light receiving elements R1 to R3 output signals indicating the presence or absence of detection of light irradiated from the light emitting elements S1 to S3 (hereinafter referred to as irradiation light). The signal is input to the control unit 90.

  When the fixing belt 62 is positioned between one or a plurality of the light emitting elements S1 to S3 and the light receiving elements R1 to R3, the fixing belt 62 causes the rays T1 to T3 of the light emitted from the light emitting elements S1 to S3 to the light receiving elements R1 to R3. Either or a plurality of the light receiving elements are blocked, and the irradiation light is not detected by any or a plurality of the light receiving elements R1 to R3. Therefore, the detection pattern of the irradiation light by the light receiving elements R <b> 1 to R <b> 3 of the photosensor 66 changes according to the position in the width direction of the fixing belt 62.

  In the following description, with respect to the position of the end portion in the width direction of the fixing belt 62 on the side where the photo sensor 66 is provided, the outside of the ray T1 with respect to the fixing belt 62 is the A1 region, and between the rays T1 and T2. Is the A2 region, the region between the rays T2 and T3 is the A3 region, and the region inside the ray T3 is the A4 region.

FIG. 7 shows the correspondence between the light detection presence / absence patterns of the light receiving elements R1 to R3 of the photosensor 66 and the position in the width direction of the fixing belt 62 shown in FIG. In FIG. 7 and the following description, the case where each of the light receiving elements R1 to R3 detects irradiation light is ON, and the case where it is not detected is OFF.
As shown in FIG. 7, the fixing belt 62 is located in the area A4 in FIG. 4 when the light receiving elements R1 to R3 are all ON with respect to the position in the width direction. Similarly, when the light receiving elements R1 and R2 are ON and the light receiving element R3 is OFF, the light receiving elements R1 and R2 are located in the A3 region of FIG. When the light receiving element R1 is ON and the light receiving elements R2 and R3 are OFF, it is located in the A2 region of FIG. When all of the light receiving elements R1 to R3 are OFF, they are located in the A1 region of FIG.

  Operation control of the photosensor 66 is performed by the control unit 90. The controller 90 measures the position of the fixing belt 62 in the width direction by operating the photo sensor 66.

  The controller 90 recognizes the position of the fixing belt 62 in the width direction based on the signal from the photo sensor 66. The control unit 90 controls the rotation angle of the steering roller 65 based on the position of the fixing belt 62 in the width direction. At this time, the control unit 90 determines whether or not the sheet P is located in one or both of the transfer nip G1 and the fixing nip H1 based on the detection signal of the sheet position detection unit 80, and the steering control amount table according to the determination result. Call. Hereinafter, the steering control amount table will be described with reference to FIGS.

FIG. 8A shows a steering control amount table.
The steering control amount table is a table showing the correspondence between the position in the width direction of the fixing belt 62 and the amount of change in the rotation angle of the steering roller 65 by the control unit 90. The steering control amount table is stored in the ROM 93, and is called and read by the CPU 91 when the rotation angle of the steering roller 65 is controlled by the control unit 90. In the steering control amount table of FIG. 8A and the following description, the state where the paper P is sandwiched at the same time in both the transfer nip G1 and the fixing nip H1 is “paper restrained”, otherwise, that is, the transfer nip G1 and the fixing. A state in which the sheet P is not sandwiched in any of the nips H1 or a state in which the sheet P is sandwiched in one of the transfer nip G1 and the fixing nip H1 is referred to as “no sheet restraint”.

  FIG. 8B shows the correspondence relationship between the change amount of the rotation angle of the steering roller in the steering control amount table and the shaft angle of the steering roller 65 in a tabular form. The shaft angle in FIG. 8B indicates the rotation angle of the rotation shaft of the steering roller 65. With respect to the rotation angle, in the positional relationship between the fixing belt 62 and the steering roller 65 shown in FIG. 5, the angle orthogonal to the operation direction F of the fixing belt fixing 62 is 0 [degree], and the rotation angle in the negative direction is − (minus). And the rotation angle in the plus direction are defined as + (plus) angles. In the following description of the fixing belt 62, as shown in FIG. 8B, the control for changing the rotation angle of the steering roller 65 to 0 and 1 [degree] is changed in two steps and 2 [degree]. Control is in four stages.

  The control unit 90 controls the change amount of the rotation angle of the steering roller 65 based on the position in the width direction of the fixing belt 62, the presence / absence of paper pinching by the transfer nip G1 and the fixing nip H1, and the steering control amount table.

When there is no paper restraint, the control unit 90 rotates the steering roller 65 in the -4 stage, -2 stage, +2 stage, and +4 stage with respect to the fixing belt 62 located in the area A1 to A4. Move angle control.
On the other hand, the control unit 90 sets the change amount of the rotation angle of the steering roller 65 to 0 regardless of the position of the fixing belt 62 when the paper is restrained. That is, the control unit 90 does not change the rotation angle of the steering roller when there is paper restraint.

  As described above, the rotation angle of the steering roller 65 is changed when there is no paper restraint, and thereby the position correction of the fixing belt 62 in the width direction is performed.

  On the other hand, if the rotation angle of the steering roller 65 is changed while the paper P is sandwiched between the transfer nip G1 and the fixing nip H1, the rotation of the rotation fixing member 61 and the fixing belt 62 causes the paper P to be fed. The sheet P may be distorted or wrinkled by receiving the pressing force and the movement vector in the width direction of the fixing belt 62 at the same time. Therefore, the control unit 90 does not change the rotation angle of the steering roller 65 when there is paper restraint.

  Next, processing relating to operation control of the image forming apparatus 1, particularly control relating to control of the rotation angle of the steering roller 65 will be described with reference to the flowchart of FIG.

  When the image forming apparatus 1 starts forming an image on the paper P, the control unit 90 operates the fixing belt 62 (step S1).

  The control unit 90 operates the photo sensor 66 to measure the belt position (step S2). The light receiving elements R1 to R3 of the photosensor 66 output signals indicating the presence or absence of light detection. The control unit 90 recognizes the position of the fixing belt 62 in the width direction based on the signal input from the photo sensor 66 (step S3).

  The controller 90 determines whether or not the paper P is in the fixing nip H1 and the transfer nip G1 based on the presence or absence of a detection signal from the paper position detector 80 (steps S4 and S5). When the paper P is in the fixing nip H1 at the same timing (step S4: YES) and in the transfer nip G1 (step S5: YES), that is, the paper P is both in the transfer nip G1 and the fixing nip H1. Are simultaneously sandwiched between the two, the control unit 90 refers to “paper restrained” in the steering control amount table (step S6).

  The control unit 90 changes the rotation angle of the steering roller 65 based on the position in the width direction of the fixing belt 62 recognized in step S3 and the change amount of the rotation angle of the steering roller 65 by the control unit 90 referred to in step S6. The stepping motor 75 is controlled so that the amount of change in the rotation angle of the “paper-restrained” steering roller 65 referred to in step S6 is zero regardless of the position of the fixing belt 62 in the width direction. Therefore, the control unit 90 does not change the rotation angle of the steering roller (step S7).

  When the paper P is in the fixing nip H1 (step S4: YES) and not in the transfer nip G1 (step S5: NO), or when the paper P is not in the fixing nip H1 (step S4: NO), control is performed. The unit 90 refers to “no paper constraint” in the steering control amount table (step S8).

  The control unit 90 changes the rotation angle of the steering roller 65 based on the position in the width direction of the fixing belt 62 recognized in step S3 and the change amount of the rotation angle of the steering roller 65 by the control unit 90 referred to in step S8. The stepping motor 75 is controlled to do so (step S9).

  After the processing in step S7 or step S9, the control unit 90 repeats the processing in steps S2 to S10 when the fixing belt 62 continues to operate (step S10: YES). When the fixing belt 62 is stopped (step S10: NO), the belt position measurement by the photo sensor 66 is ended (step S11), and the process is ended.

  4 to 9 and the configuration related to the change control of the rotation angle of the steering roller 65 and the configuration related to the detection of the position of the fixing belt 62 in the width direction by the photo sensor 66 are the steering roller 54, the photo sensor 55, and the secondary transfer belt. The same applies to the relationship 51. The turning angle of the steering roller 54 is displaced by the driving of the stepping motor 76.

  According to the above-described embodiment, the control unit 90 does not change the rotation angle of the steering roller 65 when there is paper restraint. Accordingly, there is no distortion or wrinkle of the paper P that may occur when the fixing belt 62 is moved in the width direction with the paper restrained. In addition, the control unit 90 controls the stepping motor 75 so as not to change the rotation angle of the steering roller 65 only when the paper is restrained, that is, when the paper is sandwiched between the transfer nip G1 and the fixing nip H1. To do. Accordingly, even when a sheet is sandwiched between one of the transfer nip G1 and the fixing nip H1, the control unit 90 corrects the fixing belt 62 in the width direction and continues the image forming process on the sheet P. Control. As a result, the time during which the position correction of the fixing belt 62 in the width direction is not performed can be minimized, and the position correction can be sufficiently performed without timing of paper restraint. Therefore, image formation is performed to perform the position correction. There is no interruption. Therefore, it is possible to provide an image forming apparatus with high productivity without causing paper distortion.

  Further, the fixing belt 62 is stretched by the steering roller 65, and the position of the fixing belt 65 in the width direction is changed by changing the rotation angle of the steering roller 65 by the steering roller angle changing unit 70. Since the steering roller 65 can arbitrarily guide the fixing belt 62 in the width direction of the fixing belt 62 by the rotation angle, the position of the belt can be reliably controlled according to the rotation angle of the steering roller 65.

  Further, the control unit 90 does not change the rotation angle of the steering roller 54 when the paper is restrained. Accordingly, there is no distortion or wrinkle of the paper P that may occur when the secondary transfer belt 51 is moved in the width direction in a state where there is paper restraint. In addition, the control unit 90 controls the stepping motor 76 so as not to change the rotation angle of the steering roller 54 only when the paper is restrained, that is, when the paper is sandwiched between the transfer nip G1 and the fixing nip H1. To do. Accordingly, even when a sheet is sandwiched between one of the transfer nip G1 and the fixing nip H1, the controller 90 corrects the width direction of the secondary transfer belt 51 and continues the image forming process on the sheet P. Control to do. As a result, the time during which the position correction in the width direction of the secondary transfer belt 51 is not performed can be minimized, and the position correction can be sufficiently performed at a timing without paper restraint. The formation is not interrupted. Therefore, it is possible to provide an image forming apparatus with high productivity without causing paper distortion.

  Further, the transfer belt 51 is stretched by the steering roller 54, and the position of the transfer belt 51 in the width direction is changed by changing the rotation angle of the steering roller 54 by the steering roller angle changing unit 70. Since the steering roller 54 can arbitrarily guide the transfer belt 51 in the width direction of the transfer belt 51 according to the rotation angle, the position of the belt can be reliably controlled according to the rotation angle of the steering roller 54.

  The embodiment of the present invention should be considered that the embodiment disclosed this time is illustrative and not restrictive in all respects. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

FIG. 10 is a detailed cross-sectional configuration diagram of a secondary transfer unit and a fixing unit of an image forming apparatus according to another embodiment. In addition, about the structure similar to the above-mentioned embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.
For example, as shown in FIG. 10, an image forming apparatus according to another embodiment of the present invention transfers a sheet P sandwiched in cooperation with the intermediate transfer belt 43b instead of the secondary transfer belt 51 of the above embodiment. You may have the secondary transfer roller 59 etc. which form nip. In this case, control in the width direction of the fixing belt 62 is performed by controlling the change amount of the rotation angle of the steering roller 65, and the change amount control of the rotation angle of the steering roller 54 is performed in the same manner for the secondary transfer belt 51. Is not done.

  It goes without saying that the configuration of each part of the image forming apparatus in each of the above embodiments can be replaced with another configuration without departing from the characteristics of the present invention. For example, an image forming apparatus using another image carrier (for example, a photosensitive drum shown in FIG. 11) instead of the intermediate transfer belt 43b can be used.

  The image forming apparatus may have another sensor instead of the photo sensor 66 for measuring the position of the fixing belt 62 in the width direction. For example, a sensor that has a member that contacts an end portion in the width direction of the fixing belt 62 and can measure the position in the width direction of the fixing belt 62 based on the presence or absence of contact with the member may be used. Moreover, you may use together such a sensor and a photo sensor. The same applies to the photosensor 55.

  The paper position detection unit 80 is a photo sensor that detects the paper P passing between the light emitting element and the light receiving element, but it goes without saying that other forms may be used as long as the presence or absence of the paper P can be recognized. For example, a pivotable lever member is provided in the transport path of the paper P, and when the lever comes into contact with the end of the paper P to be transported, the paper P is detected to pass by rotating in the transport direction of the paper P. The structure etc. to perform may be sufficient.

  In the image forming apparatus 1, one control unit 90 controls the amount of change of the rotation angle of both the steering rollers 54 and 65. The control unit for controlling the amount of change of each rotation angle is individually provided. It may be provided.

  It goes without saying that various numerical values such as the change amount of the rotation angle of the steering roller and the rotation direction are merely examples, and can be changed as appropriate.

  The steering roller need only be provided so that its angle can be changed with respect to a belt (such as a fixing belt or a secondary transfer belt), and is not limited to the configuration of the steering roller angle changing unit 70 in the above embodiment. For example, a configuration may be employed in which both ends of the steering roller are rotated so as to face each other, and the steering roller is rotated with the substantially center position of both ends as a rotation center.

  In the above-described embodiment, when the paper is restrained, the rotation angle of the steering roller 65 is not changed by reading the steering control amount table in which the change amount is 0 at all positions in the width direction of the fixing belt 62. Although the position correction in the width direction of the fixing belt 62 is not performed, the rotation angle of the steering roller 65 is not changed when the paper is restrained, and the position correction in the width direction of the fixing belt 62 is not performed. Other processing procedures may be taken. For example, when there is paper restraint, the steering angle may not be changed without reading the steering control amount table. The same applies to position correction in the width direction of the secondary transfer belt 51 by controlling the rotation angle of the steering roller 54.

1 is a schematic cross-sectional configuration diagram of an image forming apparatus according to a first embodiment. 2 is a functional block diagram of the image forming apparatus. FIG. It is a detailed cross-sectional block diagram of a secondary transfer part and a fixing part. It is a perspective block diagram of a steering roller angle change part. FIG. 4 is an explanatory diagram illustrating a relationship between a shaft angle of a steering roller and a fixing belt when viewed from a V direction in FIG. 3. FIG. 4 is a WW sectional view of FIG. 3 showing the positional relationship between the photosensor and the fixing belt. 7 is a correspondence table between the presence / absence pattern of light detection of the light receiving elements R1 to R3 of the photosensor and the position in the width direction of the fixing belt shown in FIG. It is a figure regarding a steering control amount table. FIG. 8A is a table showing the steering control amount table, and FIG. 8B is a table showing the correspondence between the steering roller control amount and the shaft angle of the steering roller in the steering control amount table. It is a flowchart which shows the process regarding control of the rotation angle of a steering roller. FIG. 6 is a detailed cross-sectional configuration diagram of a secondary transfer unit and a fixing unit of an image forming apparatus according to another embodiment. FIG. 10 is a diagram illustrating an outline of a transfer unit and a fixing unit of a conventional image forming apparatus. 6 is a diagram illustrating an example of a case where distortion occurs in the paper P. FIG.

Explanation of symbols

51 Secondary Transfer Belt 54 Steering Roller 55 Photo Sensor 61 Rotation Fixing Member 62 Transfer Belt 65 Steering Roller 66 Photo Sensor 70 Steering Roller Angle Changing Unit 75, 76 Stepping Motor 80 Paper Position Detection Unit 90 Control Unit 93 ROM

Claims (5)

A transfer unit provided on the upstream side in the conveyance direction of the paper and having a transfer nip; a fixing unit provided on the downstream side in the conveyance direction and having a fixing nip by a fixing belt; and a fixing belt position change for changing a width direction position of the fixing belt A mechanism unit, and a control unit that controls the fixing belt position changing mechanism unit according to the position in the width direction of the fixing belt,
The control unit does not change a position in the width direction of the fixing belt when the sheet is sandwiched between both the transfer nip of the transfer unit and the fixing nip of the fixing unit. apparatus.   The fixing belt position changing mechanism includes a first steering roller that stretches the fixing belt, and changes a position in the width direction of the fixing belt by changing a rotation angle of the first steering roller. The image forming apparatus according to claim 1, wherein: The transfer unit having a transfer nip by a transfer belt, and a transfer belt position changing mechanism unit that changes the width direction position of the transfer belt,
The control unit does not change a position in a width direction of the transfer belt when the sheet is simultaneously sandwiched between both a transfer nip of the transfer unit and a fixing nip of the fixing unit. The image forming apparatus according to 1 or 2.   The transfer belt position changing mechanism includes a second steering roller that stretches the transfer belt, and changes the width direction position of the transfer belt by changing the rotation angle of the second steering roller. The image forming apparatus according to claim 3.   The image forming apparatus according to claim 1, wherein the transfer unit has a transfer nip formed by a transfer roller.

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